- journal_title：American Mineralogist
- Contributor：Péter Németh ; Stephen W. Lehner ; Michail I. Petaev ; Peter R. Buseck
- Publisher：Mineralogical Society of America
- Date：2013-05-01
- Format：text/html
- Language：en
- Identifier：10.2138/am.2013.4459
- journal_abbrev：American Mineralogist
- issn：0003-004X
- volume：98
- issue：5-6
- firstpage：1070
- section：Letters
We report the first occurrence of kumdykolite in a meteorite (Sahara 97072, EH3). This orthorhombic form of albite occurs in the core of a concentrically zoned metal-sulfide nodule. In contrast to the terrestrial kumdykolite, the meteoritic sample has a domain structure that is consistent with either orthorhombic (Pmnn) or monoclinic (P2<sub>1sub>) space groups. The two symmetries are indicated by the presence or lack, respectively, of h + k = 2n + 1 reflections in [001] selected-area electron diffraction patterns, effects that likely result from different Si-Al ordering. Pmnn kumdykolite has only one tetrahedral site for Si and Al, whereas P2<sub>1sub> kumdykolite would have three tetrahedral sites for Si and one for Al. We propose that kumdykolite formed above 1300 K and cooled rapidly enough to preserve its unique structure. Apparently, the cooling rate varied on the scale of nanometers allowing the local development of Si-Al ordering.